Postmovement Beta Synchronization Induced by Speed Effects on IHI from the Ipsilateral to Contralateral Motor Cortex

Area of Science:

• Neuroscience
• Motor Control
• Brain Oscillations

Background:

• Beta event-related spectral perturbation (ERSP) includes movement-related beta desynchronization (MRBD) and post-movement beta synchronization (PMBS).
• Interhemispheric coherence during movement is hypothesized but not fully understood, particularly the effect of movement speed on coupling during PMBS.

Purpose of the Study:

• To investigate interhemispheric (directed) coherence and coupling during unilateral index finger abduction movements at different speeds.
• To explore the causal relationship between interhemispheric inhibition (IHI) and interhemispheric coupling during the PMBS phase.

Main Methods:

• Simultaneous electroencephalography (EEG), transcranial magnetic stimulation (TMS), and electromyography (EMG) in eight healthy volunteers.
• Analysis of interhemispheric coherence and directed coherence during ballistic and self-paced index finger abduction.
• Measurement of interhemispheric inhibition (IHI) from the ipsilateral to the contralateral motor cortex.

Main Results:

• Interhemispheric coherence was significantly higher during the PMBS period compared to the MRBD period.
• Ballistic movements induced greater interhemispheric coherence during PMBS but not MRBD.
• Directed coherence showed a contralateral to ipsilateral dominance during MRBD, reversing during PMBS, with stronger ipsilateral to contralateral coherence in ballistic movements.
• Interhemispheric inhibition (IHI) from IM1 to CM1 was stronger during PMBS peak, enhanced by ballistic movement, and negatively correlated with PMBS.

Conclusions:

• Interhemispheric coupling is prominent during PMBS, particularly with faster, ballistic movements.
• Movement speed significantly influences interhemispheric coupling and inhibition dynamics during the post-movement phase.
• Findings advance understanding of neural mechanisms underlying interhemispheric communication during motor tasks.